1. Field of the Invention
The present invention relates to a probe card for performing electrical properties confirmation tests (wafer test) for semiconductor integrated circuits, display tests for display devices, operation test for electronic circuit boards, and other such test for semiconductor integrated circuits, and for performing circuit adjustments. The present invention also relates to a test apparatus having the probe card.
2. Description of the Related Art
Conventionally, in the field of semiconductor manufacturing, electrical operation testing of multiple circuit devices in a semiconductor wafer state is performed using measurement equipment called a probe card. FIG. 7 is a plan view illustrating a conventional probe card. With conventional probe cards, electrode pads 12 are disposed at set intervals on the perimeter of the upper face of circuit devices 11 (semiconductor integrated circuits) which are unit blocks of a semiconductor wafer, and multiple probe needles 1 through 10 of the probe card are arrayed such that the tops thereof come into contact with each of the electrode pads 12. Further, the probe card comprises a circuit board 101 with the center portion thereof opened, with the rear ends of the multiple probe needles 1 through 10 to come into contact with the electrode pads 12 of the circuit device 11 attached thereto. A testing apparatus (not shown) is connected to the probe card, so that the test results can be recorded, displayed, etc. Also, arrangements are made wherein a metal resistor is provided in the circuit device 11 beforehand, and an electrical current is applied from the probe card so as to melt the metal resistor and change the resistance value thereof, or wherein a redundant circuit is provided in the circuit device 11 beforehand with a diode, and voltage is applied from the probe card to cause a short-out and make a detour to adjust the semiconductor integrated circuit.
With such probe cards, performing tests by bringing the probe needles 1 through 10 into contact with the electrode pads 12 of the semiconductor integrated circuit may meet instances wherein an insulating film (oxidized film) exists between the electrode pads 12 and the probe needles 1 through 10, which raises the contact resistance, leading to the problem of erroneous measurements. This problem is being dealt with by pressing the probe needles against the electrode pads so as to break through the oxidized film on the surface of the electrode pad and realize contact with a newly-formed surface, but this causes a problem in that the oxidized film that has been scraped off accumulates between the electrode pads 12 and the probe needles 1 through 10, so prolonged use is not possible.
An example of a probe guard for solving the above problems, invented by the present assignee, is disclosed in Japanese Unexamined Patent Application Publication No. 11-148947. This takes advantage of the fact that the electrode pads 12 exhibit shearing deformation only in a particular crystal orientation at the time of pressing the probe needles against the electrode pads 12 of the circuit device 11, such that causing shearing deformation always keeps a newly-formed surface of the electrode pads in contact with the tips of the probe needles, so that testing can be performed for prolonged periods in a stable manner, without raising contact resistance. This probe needle takes into consideration the angle of contact between the probe needle and electrode pad to effect the shearing deformation, so the shape of the tip of the probe needle has been changed from the conventional flat form to a spherical form, and the radius of curvature r of the surface of the spherical form is set with regard to the thickness t of the electrode pad such that the expression 9t≦r≦35t holds.
Also, FIG. 8 is a cross-sectional diagram illustrating another conventional probe card disclosed in Japanese Unexamined Patent Application Publication No. 6-18560. This probe card has the rear end of a probe needle 1 which comes into contact with an electrode pad 12 on the surface of a circuit device 11 attached to a circuit board 101, with the probe needle 1 further provided with an ultrasonic vibrator 21, coil 22, and ultrasonic oscillator 23, so as to break through the oxidized film by applying vibrations to the probe needle 1 and thus secure stable electrical contact.
Also, maintenance processing has been performed for scrubbing (sliding sideways on the electrode faces on the semiconductor integrated circuit) adhered aluminum in a state of being mechanically engaged with the tip of the probe needle 1 so as to eliminate the adhered aluminum.
However, with the above-described conventional probe card, in the event of applying a great current, such as 1 A or greater, the electrical resistance between the probe needle 1 and the electronic pad 12 is great at the plane of contact, so there has been the problem of heat thereat. For example, in the event that the tip of the probe needle 1 oxidizes and the contact resistance at the electrode pad reaches several ohms or more, the temperature reaches or exceeds the melting point of aluminum (approximately 660° C.), of which the electrode pad 12 is composed, due to the Joule heat thereat, so the aluminum melts and adheres to the tip of the probe needle 1. The aluminum which has adhered by the above-described melting cannot be eliminated by ultrasonic vibration or scrubbing processing, and once the melding and adhesions of aluminum occurs, the surface thereof oxidizes and the contact resistance thereof becomes high, to the extend that heat is readily generated a current values under 1 A as well. Repeating such testing unavoidably results in accumulation of aluminum on the tip of the probe needle, to the point that finally all conductivity is lost.
Also, attempts to reduce the contact resistance and suppress generation of heat by applying a weight load to the probe needle 1 so as to secure area of contact with the electrode pad 12, but this resulted in a problem in that cracks occur in the circuit device 11 due to the load in the event that the tip form of the probe needle 1 changes due to adhesion of aluminum in particular.
Also, in the event that the area of contact becomes to great due to increasing the diameter of the tip of the probe needle 1, the heat generated can be decreased, but the contact resistance becomes great after repeated tests, leading to the problem of accelerated increase in the amount of heat generated, causing the problem of melting and adhesion of aluminum.